Sound-reproducing apparatus



July 5 1927.

M. M. GRUBER SOUND REPRODUC I NG APPARATUS Filed June 14, 1920 v over the end of the flange 17.

The back of the sound box 1 coi'nprises a circular plate having a shoulder 11 extending around its periphery. An annulus 12 is adapted to fit against the shoulder 11, and when in position forms a part of the back plate 10. The outer periphery of the annulus is coextensive with the periphery of the plate, and the diameter of the back. as a whole, is somewhat less than that of the opening in the flange 7 A groove 13 similar in shape to the groove 8 is formedin the periphery of the back. Halt of the groove 13 is formed in the plate 10, and half in th annulus 12. That portion of the gasket 9 which projects beyond the edge of the flange 7 is positioned within the groove 13.

In assembling the parts justabove *de scribed the gasket 9 is placed within the groove 8. The plate 10 is placed in position with its portion of the groove 13 resting against the gasket. The annulus 12 is inserted from the front and positioned on the shoulder 11. The groove member on the annulus will bear against the gasket. The annulus may be secured to the plate 10 in any desired manner.

A notch 14 is formed in the rear face of the frame member 3, and a similar notch 15 is formed in the rear face of the plate 10.

When the member land the plate are assembled with the notches 14; and 15 in opposition a circular recess willbe formed and oll'er communication from the grooves; 8 and 13 through the back of the soundbox.

lVhen the gasket 9, which is normally circular in cross section, is forced into, the grooves S and 13 its cross sectional shape will be altered. It will become flattened. That portion of the gasket opposite the notches ll and 15 will not be confined at that point but will be forced into the recess formed by the notches and form a projection 16 which will prevent relative rotation of the member 3 and the plate 10. v

The back of the plate 10 is provided with an annular flange 17 within which the flanged end 2 of the sleeve 1 enga es. A gasket 18 is disposed between the flange 1 and the plate 10, and a similar gasket 19 is disposed between the opposite side, of the flange 1 and a cap 20 secured in place The usual means are provided for preventing relative rotation of the back 10 and the sleeve 1.

In Fig. t I have shown a modification in which two gaskets 21 and 22 are disposed between the member 3 and theplate 10, In the modification a two part'annulus 23 is interposed between the member and the plate, and in effect forms a part of the plate. The members otthe annulus. 23 are secured together to retain the gaskets in position by means of screws 24 or otherwise.

In I have shown a modified form of a bar 31 which may be secured by solder or otherwise in the groove 32, formed in the underside of the flattened extension ot member 3. Instead of the knife edges, as shown in Fig. 3, Lin this case, employ pivot or bearing points 33, 33,. such pivot or hearing points being integral with the bar, and likewise kept in perfect alignment.

InI ig. 6, I have illustrated a detail sectional view of modified form of gasket which may be utilized between the members 3 and 10 3 and 1, and the sleeve 1 and the frame. This gasket comprises a hollow tubular member as before, within which is in serted a stiffening core 31. The insertion 01 said core will prevent the collapsing of the tubular gasket, and hence retain the same always in an expanded condition, so as to firmly and securely retain and hold the mem hers in relative osition. The core may be in the form '0 a helical spring, as shown, orit may be of a length of wire which will till the bore of the tubular gasket.

T he second feature of my invention is the manner in which the stylus arm 25 is pivoted on the member 3. The stylus arm is secured at its lower end to the usual yoke 26 which in turn carries the usualsocket 27 for receiving the Sty] us (not shown). The ends of the yoke are provided with the usual angular grooves 28 for the reception of the knife edges 29, 29 carri'ed by the meinber 3 whereby the stylus arm ispivoted on the member 3 .with the minimum of friction. The usual springs 30 are provided for holding the yoke in vengagen'ient with the knife edges.

The knife edges 29 are formed on a bar 31 which is secnred by soldering or otherwise, in a groove 32 formed in the underside of a flattered extension on the member 3. The knife edges being integral withth'e bar 31 may be made in erfect alineinent. The downturned ends 0 the bar forming the knife edges may be hardened, or the entire bar maybe hardened. The bar 31 being, as it is, of considerable bulk may be soldered or brazed inthe groove 32 and the heat of the solder will not be sufficient to draw the temper of the knife edges.

In operation the back plate the sound box may move relatively to the member 3 due to airvibrations. set up by the diaphragm. The back plate may move away frotn'the member?) due to the cushioning eilectrof the gaskets 9, 18 and 19. or the ring 3 may be moved away from the back due to I the flexibility of the gasket 9. In either case scratchy tones will be eliminated.

Instead of the hollow gaskets plastic rubber may be employed. 7

In accordance with the provisionsot the patent statutes, I have described the prin oiple of my invention together with the apparatus which I now consider to represent thebest embodiment thereof, but I desire it understood that my invention is not confined ti l nieansof which objects of my invention are attained, and, the new results accomplished,

ashcrein set forth. as it is obvious that the particular embodiment herein shown and described only one of many that can be employed to attain these objects and accomplish these results.

Having now described my invention, what I claim and desire to secure byLetters Patcut, is:-- a

1,. In a sound box, a supporting member, a supported member mounted upon the perimeter of said supporting member, tubular cushioning spacing rings interposed between said members, means for compressing said rings in an axial direction whereby said rings will'beexpanded in a diametrical di rection, recesses in the adjacent peripheral surfaces of saidmembers, permitting expansion of portions of said rings into said recesses whereby said members are locked against relative rotation.

2. In a sound. box, a plate, a casing surroundlngsaid plate, said caslng having a minimum diameter greater than the maximum diameter of said plate, annular means between the plate and the casing, comprising grooves in their adjacent faces, and resiL ient,tubular means seated in thegrooves, and means for compressing said tubular'means to illiptical cross-section.

3. In a sound box, a plate, a casing surrounding said plate, said casing having a minimum diameter greater than the maximum diameter of said plate, annular means between the plate and'the casing, comprising grooves in their adjacent faces, and resilient, tubular means seated in the grooves, and means contacting with said tubular means to compress the same.

This specification signed this 28th day of May, 1920.

MORRIS M. GRUBER. 

